A conventional pneumatic nailer generally includes a body with a barrel which is connected to a magazine in which nails are received. The nails are urged by a spring so as to be pushed into the barrel to be fired by an impact pin which is driven by pneumatic power. A safety bar is movably connected to the nailer and connected to a trigger mechanism such that the trigger can be pulled to fire the nails only when the safety bar is pushed against the object to be nailed. The safety bar effectively reduces risks of unintentional activation of the trigger mechanism. Nevertheless, the safety bar does not have any locking device to prevent it from being pushed even when there is not a nail in the barrel. Under this circumstance, if the safety bar is pushed, the trigger mechanism can be activated although no nail is ejected from the barrel. The impact pin moves by the pneumatic power and could hit the surface of the object to which the safety bar pushes against. This could damage the impact pin and/or the surface of the object.
The present invention intends to provide a safety device that has a pin urged by a spring and the pin locks the safety bar when no nail is located in the barrel such that the safety pin cannot be pushed backward.